kickpanel speaker locations : pros, cons

I figured I'd start a thread about the pros & cons of kickpanel speaker locations, because there seems to be a lot of misinformation on the topic floating around this forum Please allow me to first say that I'm not a huge fan of kickpanel installations ... mostly because I find them to be ugly and intrusive ... and for the record I will absolutely admit that I have not heard the finest incarnation of the art, realized by some of the best installers/tuners in the biz. I hope to correct that sometime soon.

A brief review of dominant hearing mechanisms is in order. For the purposes of this discussion, it's VERY important to decompose hearing localization into two dimensions : lateral and vertical. I think the most important points are these :

1. Localization cues in the lateral plane are dictated by the differences in the acoustic transfer function to our two ears. These include inter-aural time differences, mostly significant for lower frequencies in the midbass and lower midrange, and inter-aural level differences, mostly significant for higher frequencies in the upper midrange and treble.

2. Localization in the vertical plane is dictated primarily by the shape of our outer ears and torso. Please consider that, if our outer ears and torsos were absent, we would be left with the classic "sphere with holes in the sides" for our heads ... and the symmetry of this geometry would absolutely dictate that vertical localization would be impossible. It's my understanding that the outer ear has the largest impact on the acoustic transfer function for vertical localization ... and given the dimensions of the outer ear, this implies that vertical localization cues are only significant above ~1kHz or so.

To summarize :

1. Ears are on the sides of our heads. Through ITD, IID we use both ears for left/right cues.

2. Vertical cues are given to us by the shape of our outer ears ... not vertically symmetrical, thank you, but common to both ears ... and the corresponding impact on the acoustic transfer function to our eardrums.

Conclusions : Let's say as an audio enthusiast, you happen to care about a realistic soundstage in your vehicle ... laterally as well as vertically. Furthermore, let's say you happen to care about a realistic soundstage for both front seat passengers, at the same time (For what it's worth, this ain't me ... I'm lazy, unskilled in fabrication, and selfish). Here's why kickpanels make sense in this case :

1. Left, right pathlength differences cannot be ELECTRONICALLY compensated for both front seat passengers at the same time. Simply not enough degrees of freedom, for the four ears involved. Kickpanels almost always present the best choice for PHYSICALLY equalizing PLD's.

2. Vertical cues can be electronically compensated, by a specialized form of equalization known as head-related transfer function inversion and substitution. A great reference on this topic is :

Creating Source Elevation Illusions by Spectral Manipulation, by P. Jeffrey Bloom, JAES, vol. 25, pp.820-828, September 1977.

So, simply put, the kickpanel optimization suggests that you solve the left/right problem physically, since it can't be solved electronically for both front seat passengers. The price you pay is in stage height ... but this can be solved electronically for both front seat passngers And yes, the best installers and tuners have known all this for many, many years.

Incidentally, there's another interesting conclusion to be drawn : physical separation of drivers in any single channel ... like mid & tweet, for example ... is not necessarily the horror of horrors it's often considered to be, particularly if the separation is vertical. Either the ear can't tell to begin with, since vertical localization cues don't even start until the treble, or spectral manipulation (EQ) can be employed to very convincingly trick the ear. Check the AES reference above. One of the most convincing soundstages I've ever heard ... with no obvious penalties in tonality, or coherence ... had midranges in the kicks and tweets in the A-Pillars. And I'm far, far from alone on this one

Armed with that background, perhaps we can list some kickpanel pros & cons :

Pros :

- Most convincing lateral soundstage for both front seat passengers at the same time.

- Early reflections ... floor, underdash ... are relatively easy to tame, compared to windshield reflections of higher-mounted drivers, for example.

Cons :

- Often ugly and intrusive (to me, anyway)

- Establishing vertical stage height requires clever EQ ... spectral manipulation, involving HRTF inversion and substitution.

- Early diffraction caused by feet and legs.

Now it may be, that some users don't care at all about staging ... only tonality. There's plenty of room for everyone in this hobby

[edwelly]

Let's say you are installing a system in Honda Accord 2003 EX 4 dr- where would you put the speakers?
I choose this car because I have seen both kick and doors done.

[bassfromspace]

I know more than werewolf, I just keep quiet most times.

[npdang]

This is a great write up. Definitely needs to be moved to the tech. articles forum.

[Thoraudio]

I don't particularly care for fiberglass blobs on the floor either.

IMNSHO, the best kick panel installs are those that cosmetically follow the natural plane of the of the factory panels, but behind, the drivers are angled to compensate for the extreme off axis angle the near side drivers present. Scott B.s 240 being a great example.

[PlanetGranite]

Linky for a good HRTF graph here

As Werewolf mentioned, we want to take the inverse (mirror) of the graph at a specific position (i.e. - infront and below) when applying equalization.

Also, Physics Today has a damn good (although slow reading) article titled "How We Localize Sound" which can be found here .

[edwelly]

What about this install? I cannot comment on the stage presence but assuming this was a good sound stage, would the look of these be better in your eyes?
05 Tacoma Progress

PB2theMax - I hope you do not mind me using your install here. I think it looks GREAT!!!

[chuyler1]

I think that some people go a little crazy with angling the speakers. Granted some speakers have better on-axis response than off, but the difference is usually minimal and can be fixed with an EQ. Once you are willing to sacrifice the angle of the speaker in the kickpanel, you will realize it is very easy to install 3", 4" and often 5.25" speakers without taking up floor space.

When it comes to tweeters in kicks, I am not a big fan at all. All of the successful renditions of tweeter kicks I have heard were in show-vehicles that had the seats pushed back so far you couldn't drive the car. That is not practical and it defeats the entire purpose of car audio. People doing that might as well just pick up home audio as a hobby instead. With the seat in a normal driving position, the high frequencies easily reflect off your leg drawing the stage down even lower than intended. Furthermore, a passenger's leg and foot may completely block the tweeter which changes the sound of the system drastically as they shift around in the seat. So I just put my tweeters up high and as far away as possible and deal with the reflections. At least it makes for an enjoyable listening experience in any seat position with or with out a passenger.

I also have some comments about large drivers in kicks. I believe you must utilize the door locations to get any kind of midbass up front. There simply isn't enough airspace in kicks for 6.5" woofers to truely shine in this department. I tried this once and was very unhappy with the results. No amount of ventilation and polyfill could clean up the midbass region and get rid of the nasty peaks. Since then, all of my kickpanel installs have been 4-way (T,MR,MB,SW) designs with a larger woofer in the door. And since you can't utilize the lower range of a 6.5" driver mounted in a kick, you might as well stick to 3", 4", and 5.25" drivers which fit better anyway.

[3.5max6spd]

Originally Posted by Thoraudio

I don't particularly care for fiberglass blobs on the floor either.

IMNSHO, the best kick panel installs are those that cosmetically follow the natural plane of the of the factory panels, but behind, the drivers are angled to compensate for the extreme off axis angle the near side drivers present. Scott B.s 240 being a great example.

X2

Concentrating on angling the drivers toward a center focus on the dash as opposed to directly at the listener has worked wonders for my staging.

[FoxPro5]

Originally Posted by werewolf

Incidentally, there's another interesting conclusion to be drawn : physical separation of drivers in any single channel ... like mid & tweet, for example ... is not necessarily the horror of horrors it's often considered to be, particularly if the separation is vertical. Either the ear can't tell to begin with, since vertical localization cues don't even start until the treble, or spectral manipulation (EQ) can be employed to very convincingly trick the ear. Check the AES reference above. One of the most convincing soundstages I've ever heard ... with no obvious penalties in tonality, or coherence ... had midranges in the kicks and tweets in the A-Pillars. And I'm far, far from alone on this one

Now THAT'S what I wanted to hear! Thanks for the info Wolf.

Physical separation of drivers ... like mid & tweet ... probably deserves a thread of it's own. In my opinion, the old wisdom of "coherence" and "point sourcing" has ... evolved, shall we say. The more we learn about how the ear actually localizes sound, the more we learn to manipulate

Case-in-point : consider that vertical cues don't begin until maybe 1~2kHz. How can the ear possibly localize a dedicated midbass driver (up to ~200Hz, for example), in the vertical plane? Simple answer : it can't. There's a "circle of confusion" regarding the midbass ... as long as a midbass driver is generating the same ITD's to your ears, one location can't be localized, or differentiated, from another. So why would a dedicated midbass need to be physically located in close proximity to a tweet? Perhaps to satisfy your eyes ... because your ears certainly can't tell.

And of course, there's the AES-supported evidence of being able to trick the ear, vertically, by spectral manipulation based on HRTF inversion/substitution.

Now, there are certainly other things to consider when separating drivers. The interference pattern, or lobe, resulting from both drivers playing the same frequency at the crossover, for example. But once again, electronics can help : crossover alignments and slopes, parallel time alignment for "lobe steering", etc. Remember that one advantage offered by the otherwise miserable car environment is that listeners tend not to wander around the listening space!

By the way ... in my opinion and experience, the car audio fanatics have learned, and leveraged, much more about how we localize sound than home audio enthusiasts. Simply because they've had to ... in order to realize a convincing stage in a small, reflective environment where you can't possibly sit equi-distant between the speakers.

[raamaudio]

I learned this from one of the top installers in the world, a good buddy of mine.

1) Put your front seats where you intend to either drive the car or where you will have them if you plan to compete, this is very very important. I am talking about fore and aft, height, seat back tilt angle. If not competing then where you will drive the car at and the passenger side the same.
If you are competing in car audio comps, then all the way back and low but even with the passenger side for height, lean the seats back a bit but not real far to make them uncomfortable.

2) Sit in your seat as you would driving or listening as per above, make sure you are correctly placed, if you tend to drive leaning way forward like some do, you should adjust how you sit, better for your posture anyway, lol, lean back in the seat

(here is an additional hint, almost all will do better if the seats are lowered, leaned back quite a bit, etc. but in my Tacoma I had to raise the seats, go figure

3) Have somebody you trust to do this correctly, critically important. Roll the windows up, have them look very very carefully at where the entrance to your eardrum is on your window side ear, left ear, mark it on the window or on the pillar with a small spot of tape.

4) Move to the other front seat and do the same except of course on the right ear this time.

5) Ok to get out of the car now Measure 5" forward and 1.5" down from the spot marked for your ear entrance points on each side of the car, should be two marks on the car now, one for your ears and one forward and down as above.

6) Build some temp baffles for the speakers or the ones you will use, what I do. Have the tweeters mounted very low and to the door side of the baffle, the woofers go furthest forward and low as well.

7) Aim the woofers(midbasses) exactly at the forward and down spot on the glass you marked.
This is the sweet spot, instead of fighting the glass reflections you are using them to your advantage. The right speaker will reflect off the left glass into your left ear and help equalize the sound you hear from both speakers, seems odd but it works, exceptionally well. I beat a prior world champ twice in two months, two seperate installs in my truck and two totally seperate comp installs in his truck and a customers truck using these methods of alignment.

8)Take a kitchen towel and put it behind the baffels can cover the back of the speakers, then do some serious listening tests to see if you need to align them differently but this should be pretty darn accurate.

9) Be very carefull when glassing the kicks as the glass can pull them out of alignment when drying as tends to shrink so mount the baffles very well before glassing.

10) Wire the midbass on the passenger out of phase with the drivers side midbass, you may lose some midbass output but the sub can help make up for that quite well when tuned properly, better yet to have some midbasses in the doors. Try all the phasing setups you can, sometimes the drivers side is best, sometimes but not often, both in phase works)


For those not building kicks here is a simple install plan that works quite well, has been used alot in competion cars.

1) use the door locations for the midbasses, both in phase.
2) tweeters in the A pillars firing directly at each other, as wide apart as possible, both at the same exact height and about 2" above the highest point on the dash. Wire both tweeters out of phase(pos and neg wires reversed but this may have to be reconsideded depending on the midbass wiring, take your timem and try them all! Make sure to try many different aim points as well.
3) Use a dash mat, fugly but they work.

In fact, a dash mat will improve just about any install ever done, including kick panels, have one in my truck, been there for years"

I have done this in several cars and trucks over the years and always with great results.

Rick

[luvdeftonz]

werewolf, you have the rare gift of making technospeak fun and interesting to read. Most "science geeks" are boring writers. Not you. Great article and follow up comments.

[chuyler1]

Rick, that's a pretty neat way of aligning speakers and I understand the theory behind it. I think your technique can be improved somewhat by using a laser pointer and a small mirror.

1) Mount your baffle and build a bracket to sling over the opening that will hold a laser pointer so it fires straight out.
2) Follow instructions above by rick to set your listening position and sit down.
3) Hold the mirror flat against the window in roughly the spot that Rick stated.
4) Turn on the laser pointer and try to line up the angle with your ear. You will need someone to move the baffle and someone else to verify the spot on your ear. You may have to move the mirror around too but only keep it 5-10" away from your ear. If you go to close the laser will bounce off your nose, if you go to far you'll end up having to lower the mirror too much to get the right angle.

[DS-21]

I'd love to respond to this post, but my brain's done for the day. Six hours running gels and another 10 tutoring - the LSAT is next week and everybody seems to want last minute tutoring...

So this post richly needs a rebuttal, but it won't get one from me until I have the intellectual energy to put into it. Maybe October 1.

[raamaudio]

The reason for this alignment is to utilize the glass instead of fighting it.

I have used lazers, they can be helpfull to a great degree but it still takes using your ears to fine tune

I aim the tweeter pretty much to the same spot as the mids, meaning they are not on a flat plane normall. It was easy with the Rainbow Ref tweeters, for others a bit more effort to aim them. I have found just a tad of TA can make a huge difference when mounted flat on the same baffle as the mids and that is the only time I have ever used TA.

I am eager to hear 21's take on this, it will be interesting to say the least. I learned this from Matt at ID, not sure if it was his method or something from Eric.

One thing I do not do, I do not try to make a car sound like a perfect listening room, I try to make it sound as good as possible and overall I like it far better than most any listening room I have been in, just more fun!!!!!

If I want sonic perfection I listen to live music, not reproduced, though I have heard some systems that are just plain incredible, being there is always better

Rick

[Thoraudio]

Originally Posted by raamaudio

I am eager to hear 21's take on this, it will be interesting to say the least. I learned this from Matt at ID, not sure if it was his method or something from Eric.

His take will be that reasonable people only drive manual's... so kicks are stupid.

or that audio imaging is distracting. (still haven't figured that one out).

or that the audio signature of the drivers is so horribly blocked that it is more aking to chewing glass than music...

or that Steve Jobs hasn't recommened it yet...

or something equally weak.

[legend94]

RaamAudio:
Are you saying that first I should line up the mark on the window with my ear, second go 5 inches toward the front of the car and 1.5 inches down? and if my mid and tweet are mounted on the same baffle they should point to that location?

[legend94]

Originally Posted by Thoraudio

His take will be that reasonable people only drive manual's... so kicks are stupid.

or that audio imaging is distracting. (still haven't figured that one out).

or that the audio signature of the drivers is so horribly blocked that it is more aking to chewing glass than music...

or that Steve Jobs hasn't recommened it yet...

or something equally weak.

what are you thoughts?
i sense your sarcasm, but dont know the reasons behind it
im just now in the process of wanting to build kicks and want to gather all the options and opinions

[FocusInCali]

Originally Posted by Thoraudio

or that Steve Jobs hasn't recommened it yet...

boo hiss, low blow

I've always appreciated what you have to say, but that's plain ignorance speaking there.

Wether you use Mac or not, Steve Jobs deserves to be credited for creating a team of innovators.

DS-21's post in this thread will also get a response ... i hope everyone will wait with breathless anticipation until, about, mid-December when a great intellect shall return to this thread ...

... oh, thanks for the compliments guys I participate in audio forums to both teach and learn ... wonder why other guys do it?

[Hernan]

D-21's points of view are interesting and he gives a great pump to some threads. He's not always right but who are??

[03blueSI]

The problem I have with kickpanel mounted speakers is no matter how many times you tell people to be careful with the speakers they never pay attention. Sound wise they work well except for the leg blocking the tweeters. My next install I will probably go back to kick mid, door midbass and a-pillar tweet as long as I can find or build a decent grill for a 4.5" revelator.

[demon2091tb]

I'd love to hear about this ALOT more. Actually learn something about theory and such from some intelligent people.

Currently finishing up my kickpanels with a pair of DIYMA 2" domes, and LPG 26's up top in pillars, and man it sounds good, a slight delay on the tweet to me adds just a bit more depth to the stage.....while keeping everything anchored on the dash. But could we also go into not just Cones, but domes as well, as i think domes might add a little something that cones can't.

Is synching up pairs of drivers with TA ok to get a uniform PLD between all drivers on a singular plane perpindicular to the dash, basically alighning the whole soundstage to the depth of the mid under the dash.....Does this make sense and actually hold water to being a good starting point to realistic depth??